970204H IOP10 on Expected Frontal Wave Development

Aircraft Involved: P-3, Electra, UK C-130

Summary Description of Mission:

The planned primary mission was the systematic survey ("Lawnmower" pattern) on an active portion of frontal wave cyclone expected to develop in the southern part of the MSA. The P-3 and Electra departed Shannon on schedule about 0600 and 0540 UTC, respectively. The two Doppler aircraft rendezvoused with the C-130 begin the highly coordinated runs at the initial point at 0700 UTC. The first two legs of the systematic survey were basically completed in clear air, with only a narrow region near the southern turn points in, or near, a weak convective/stratiform band. During the first half of the third leg, a zone of precipitation was noted on the P-3s LF radar near 50N 16.5W which was also a region that the Ops Center (via an e-mail received by the C-130 satellite communications equipment) indicated was the expected region of "cloud head development" as an upper level PV max was predicted by the UKMO LAM model there. Based on the LF radar and model forecast, the flight tracks of the P-3 and C-130 were modified (the Electra flight plan could not be modified due to endurance limitations) to shift westward. To maintain the integrity of the "systematic survey" the P-3 track was shifted from 100 km to the east of the Electra, to 100 km to the west. The C-130 track was shifted to be down the middle of the two Doppler aircraft tracks. The new tracks nicely intercepted an advancing ENE-SSW squall line with the P-3 and Electra tracks bracketing the line, and the C-130 through the middle. Following the completion of its leg, the Electra departed the region at 1200 UTC and returned to Shannon. The P-3 and C-130 completed another leg through the western edge of the line, then the C-130 also departed. The P-3 continued to perform "Doppler boxes" around the line for another 1.5 hours. Following the completion of the Doppler patterns at 1400 UTC, (by which time the line had weakened and become a blob of stratiform rain with embedded convection) the P-3 tracked to the buoy at 51.02N, 13.33W, performed a spiral ascent to 23,000 ft, and drop a sonde to test the system. The sonde performed perfectly and the P-3 returned to Shannon at 1520 UTC.

Communications & Coordination:

1. No troubles.

P-3 Equipment Problems Encountered:

1. The P-3 Doppler radar displays seemed to occasionally show unrealistic radial velocity patterns.

Coordination Problems

1. No problems of note.

Recommendations & Evaluation:

1. Very good mission from an execution point of view. Coordination of legs was easily accomplished by speeding up and/or slowing down to syncronize each leg.

2. The last 2 legs of the P-3 and C-130, and the last leg of the Electra were within the most interesting precipitation region. The system resembed a "comma" with extensive stratiform precip behind (to the north and west) of the moving squall line.

--Dave Jorgensen & Yvon Lemaitre